This invention relates to in-situ electrochemical regeneration of alkaline hydrogen peroxide and chlorine for a continuously operating chemical oxygen-iodine laser, which can be used for high energy material processing applications.
Prior art has established that COIL (Chemical Oxygen-Iodine Laser) is capable of delivering a high power laser beam with excellent beam quality and at a wavelength compatible with optical fibers. These characteristics make COIL a candidate for a variety of industrial applications in material processing, where high power, high-brightness, and beams delivered by optical fiber can provide economic and/or technological advantages over existing industrial lasers such as carbon dioxide (CO2) and Nd:YAG lasers. High-brightness lasers with 10-25 kW power can improve existing laser oriented industrial processes and can facilitate development of certain emerging applications such as aluminum cutting and welding, thick section cutting for dismantlement of nuclear installations, laser driven x-ray lithography, and pulsed laser vapor deposition.
In COIL the laser power is produced by extraction of energy from a flow of excited gas produced by reaction of chemical fuels. Sustaining continuous operation, such as required for many industrial and government applications in material processing, requires a continuous flow of fuel must be provided. In prior art, fresh fuel obtained from commercial suppliers was used to operate COIL. However, the costs associated with providing fresh fuel and disposing of reaction products make use of COIL for industrial applications uneconomical and have been a leading impediment to developing commercially useful COIL devices.
Laser power in COIL is derived from chemical energy released by reacting Chlorine gas and Basic (alkaline) Hydrogen Peroxide (BHP), an aqueous solution of hydrogen peroxide and potassium (or sodium) hydroxide, to generate singlet oxygen which produces and excites atomic iodine to a laser transition (disclosed by McDermott in U.S. Pat. No. 4,267,526). In prior art, BHP was prepared by mixing highly concentrated solutions of hydrogen peroxide and potassium hydroxide obtained from commercial suppliers. Chlorine was also commercially obtained in a form of liquefied gas. The by-product of the BHP reaction with chlorine, namely aqueous solution of potassium chloride (which normally includes some unreacted BHP) was disposed of as a hazardous waste.
Using raw fuels in this manner to operate COIL on a continuous basis has several disadvantages. First, raw fuels are relatively expensive and their continuous supply requires significant logistics. Highly corrosive nature of the fuels requires significant safety precautions during their transport, handling and storage. Similar considerations apply to disposal of reaction by-products. In addition, due to thermal decomposition of peroxyl anions BHP has a short shelf life which precludes maintaining a large inventory for use with COIL.
Typical COIL systems operate with a predetermined quantity of BHP liquor that is continuously recirculated within the system and reacted with chlorine gas. During each contact with chlorine some of the peroxyl and hydroxyl anions in the BHP are depleted in a reaction which generated singlet oxygen as the primary product, singlet oxygen is separated as gas, and salt and water as secondary products that become a part of the recirculating BHP liquor. The reaction thus reduces concentration of peroxyl and hydroxyl anions in the liquor, increases liquor volume by addition of water, and increases its salt content.
COIL systems have been operated wherein the entire quantity of BHP required to sustain limited time operation was prepared in advance and the laser operated until the BHP concentration was reduced to the point at which the laser would no longer function efficiently, at which time the residual BHP liquor was drained and replaced with fresh liquor.
Other COIL systems have been proposed where the quantity of BHP liquor continuously recirculates within the system and reacting with chorine. The system is continuously provided with chlorine as well as fresh highly concentrated hydrogen peroxide and potassium hydroxide while removing water and potassium chloride salt. This method maintains a proper concentration of peroxyl and hydroxyl anions in the BHP liquor and allows continuous operation of a COIL laser.
In either case fresh chemical fuel required to operate the laser, namely hydrogen peroxide, potassium hydroxide, and chlorine fuel must be provided from external sources and the reaction byproducts disposed of in an environmentally safe manner. Thus a continuous operation of COIL in this fashion necessitates significant monetary expense and logistical support.
The invention is for electrochemical regeneration of Basic Hydrogen Peroxide. (BHP) and chlorine for use in a Chemical Oxygen-Iodine Lasers (COIL). Depleted (reduced peroxyl strength) BHP from the singlet delta oxygen generator is recycled through an electrochemical cell which simultaneously regenerates BHP to its full strength and produces chlorine, both for use in the singlet delta oxygen generator.
The electrochemical regenerator cell has two compartments separated by a cation-exchange membrane. In the anode compartment chlorine is produced by electrolysis of potassium chloride and in the cathode compartment peroxyl and hydroxyl anions are produced by electrosynthesis of water and oxygen. In this fashion the electrochemical cell essentially reverses the singlet delta oxygen-producing reaction between BHP and chlorine by reconstituting the original reactants. Electrochemical regeneration of BHP and chlorine allows the COIL system to operate only on electricity and atmospheric oxygen without external source of hydrogen peroxide, potassium hydroxide, and chlorine.
The use of such a regenerative system would reduce or eliminate the need to supply external sources of reactants for use in a COIL. This would reduce the time and energy used to supply such elements and the space necessary to inventory such elements for use in a COIL. Additionally, this would also reduce the cost of a COIL since only an initial external supply of reactant elements is necessary which are then regenerated within the system itself. Finally, this would also significantly reduce the amount of hazardous material produced by a COIL laser.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.